Suggest git submodule update --init --recursive (#13769)

Summary:
We now have submodules that have submodules
Pull Request resolved: #13769

Reviewed By: soumith

Differential Revision: D13000203

Pulled By: SsnL

fbshipit-source-id: 63c0c19c6c9d25ae3bf255a2421a82ca68278866

setup.py

@@ -457,7 +457,7 @@ def run(self):
         def check_file(f):
             if not os.path.exists(f):
                 print("Could not find {}".format(f))
-                print("Did you run 'git submodule update --init'?")
+                print("Did you run 'git submodule update --init --recursive'?")
                 sys.exit(1)
 
         check_file(os.path.join(third_party_path, "gloo", "CMakeLists.txt"))